Legal Question in Criminal Law in California

No. Don't ever go anywhere with the police unless you're under arrest. Never consent to a search, never answer questions (by that I mean say NOTHING AT ALL TO THE POLICE), and never agree to a "drug test." Tell them you plead the Fifth and you want a lawyer.

Police are generally required to have a warrant to come to your home and arrest you. You don't ever have to go with them voluntarily. You have the right to have a lawyer present during police questioning, and if they want to talk to you, invoke your right to remain silent and to have your lawyer present.

Be careful about refusing a drug test in custody. There are jury instructions in criminal law that allow the prosecutor to use the evidence of your refusal to submit to a drug test as proof of your guilt. I tend to advise clients who maintain their innocence and refuse to drug tests to submit to drug testing with a private accredited lab.